Generator powered bicycle headlamp and electrical circuit

ABSTRACT

A bicycle headlamp including: a rotor having a plurality of magnet plates attached to spokes of a bicycle wheel, each magnet plate including a plurality of magnets disposed at regular circumferential spacings with alternating south and north poles; and a stator including a power-generating coil disposed in a fixed position to face the magnetic pole faces of the magnet plates. A case includes at least a headlamp electrical circuit for establishing resonance with a certain relative speed of the magnets by means of the power-generating coil and a capacitor connected in series, and for rectifying, smoothing out, and outputting electric power obtained from the power-generating coil. Also included are a light-emitting diode and a condenser lens for focusing light emitted from the light emitting diode in front of the bicycle and for illuminating the roadway.

TECHNICAL FIELD

The present invention relates to bicycle headlamps which include atleast a rotor provided with magnets attached to spokes of a wheel of abicycle, a stator provided with a power-generating coil mounted to facethe rotor, a headlamp electrical circuit, a light-emitting diode, and acondenser lens, the light-emitting diode being lit by electricitygenerated by pedaling, and also relates to headlamp electrical circuits.

BACKGROUND ART

Conventional bicycle headlamps using an incandescent lamp receive powerfor providing illumination sufficient for nighttime cycling from arotary generator, to which a rotary motion is transferred by a rollerpressed against a side of a tire. This method exerts a large frictionalresistance on the rotary motion, and the cyclist feels a drag whilepedaling. Accordingly, cycling at night requires extra power. Theconventional generator using the roller to be pressed against the sideof the tire, however, must be turned on manually, and thus atrouble-free simple device has been needed.

The conventional method of pressing the roller against the side of thetire has problems. A first problem is that the roller pressed againstthe side of the tire while cycling at night incurs a frictionalresistance on the rotary motion, causing the cyclist to feel that thepedals have become heavy.

A second problem is that illumination will decrease when cycling on amuddy road because mud getting in between the tire and the roller causesthe roller to slide along the tire.

A third problem is the need to manually turn on and turn off thegenerator for cycling at night.

An object of the present invention is to provide a contactless,light-load bicycle headlamp and a headlamp electrical circuit that cansolve the problems described above by adopting new technologies.

DISCLOSURE OF INVENTION

In order to achieve the object described above, a bicycle headlampdescribed in claim 1 of the present invention is characterized byincluding a rotor including a plurality of magnet plates attached tospokes of a bicycle wheel along the circumference of the wheel, eachmagnet plate having the form of an arc of a certain circle and includinga plurality of magnets disposed at regular circumferential spacings withalternating south and north poles; a stator including a power-generatingcoil including a coil and an iron core disposed in a fixed position toface the magnetic pole faces of the magnet plates of the rotor; and acase containing at least a headlamp electrical circuit for establishingresonance at a frequency synchronized with a certain relative speed ofthe magnets by means of the power-generating coil of the stator and acapacitor connected in series with the power-generating coil and forrectifying, smoothing, and outputting electric power obtained from thepower-generating coil, a light-emitting diode which is lit by theelectric power supplied from the headlamp electrical circuit, and acondenser lens for focusing light emitted from the light-emitting diodein front of the bicycle and for illuminating the roadway.

A further feature of the present invention is a bicycle headlamp,wherein the stator has the magnet plates attached to the spokes of thebicycle along the circumference of the wheel, in a continuous ring shapeor in separate positions.

A further feature of the present invention is a bicycle headlamp,wherein the light-emitting diode is a white light-emitting diode with aluminous intensity of 2 cd or higher, and the lens has such a focallength that a certain level of illumination is ensured at a specifieddistance.

A further feature of the present invention is a bicycle headlamp,wherein a plurality of light-emitting diodes are used; the lens is adome-shaped lens disposed for each of the light-emitting diodes, thedome-shaped lens having a curvature, a diameter, and a thicknesscalculated to obtain a specified level of illumination in a specifiedcircle at a specified distance by focusing light; and a reflector isprovided on a flat-plate portion above the lens, by applying a treatmentfor producing diffused reflection, so that the approach of the bicyclecan be noticed ahead of the bicycle.

A further feature of the present invention is a bicycle headlamp,wherein the stator, including the power-generating coil, the headlampelectrical circuit, the light-emitting diode, and the condenser lens arecontained in the case as a unit.

A further feature of the present invention is a bicycle headlamp,wherein the headlamp electrical circuit, the light-emitting diode, andthe condenser lens are contained in the case; and the stator, includingthe power-generating coil, is separately disposed outside the case.

In order to achieve the object described above, a headlamp electricalcircuit of the present invention has a resonance circuit forestablishing resonance at a frequency synchronized with a specifiedrelative speed of the magnets, the resonance circuit including apower-generating coil of the stator and a capacitor connected in serieswith the power-generating coil, and a rectifying and smoothing circuitfor rectifying and smoothing electric power obtained from thepower-generating coil of the resonance circuit and for supplying theelectric power to the light-emitting diode.

A further feature of the present invention is a headlamp electricalcircuit, wherein the rectifying and smoothing circuit has a dc-dcconverter for rectifying electric power obtained from thepower-generating coil of the resonance circuit by means of a diode andfor smoothing out the electric power by means of a smoothing capacitor,and a constant-current circuit for receiving a direct current from thedc-dc converter and supplying a constant current to the light-emittingdiode, the constant-current circuit including at least two transistors,two resistors, and a capacitor.

A further feature of the present invention is a headlamp electricalcircuit, wherein a light sensor and/or a manual switch is connected tothe constant current circuit; and the constant-current circuit isconfigured to allow or interrupt current supply to the light-emittingdiode in accordance with a sense signal from the light sensor, isconfigured to allow or interrupt current supply to the light-emittingdiode in accordance with an on/off signal from the manual switch, or isconfigured to allow or interrupt current supply to the light-emittingdiode in accordance with either or both of the signal from the lightsensor and the signal from the manual switch.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view showing a bicycle headlamp according to a firstembodiment of the present invention, namely, a side view showing aplurality of magnet plates attached to spokes of a bicycle wheel atparticular spacings.

FIG. 2 is a perspective view showing a contactless, light-load bicycleheadlamp according to the first embodiment of the present invention.

FIG. 3 is an enlarged perspective view showing a rotor and a stator ofthe bicycle headlamp according to the first embodiment of the presentinvention.

FIG. 4 shows enlarged views of a part of the rotor of the bicycleheadlamp according to the first embodiment of the present invention:FIG. 4( a) is an enlarged front view of the magnet plate of the rotor;and FIG. 4( b) is an enlarged side view of the magnet plate of therotor.

FIG. 5 shows enlarged views of a magnet mounted on the magnet plate ofthe rotor of the bicycle headlamp according to the first embodiment ofthe present invention: FIG. 5( a) is a perspective view of the magnetmounted on the magnet plate of the rotor; FIG. 5( b) is a front viewshowing the magnet mounted on the magnet plate of the rotor; and FIG. 5(c) is an enlarged front view of the magnet mounted on the magnet plateof the rotor.

FIG. 6 shows enlarged views of a power-generating coil of the stator ofthe bicycle headlamp according to the first embodiment of the presentinvention: FIG. 6( a) is a front view of the power-generating coil ofthe stator; and FIG. 6( b) is a side view of the power-generating coilof the stator.

FIG. 7 is a view showing the positional relationship between the teethof the power-generating coil of the stator and the individual magnets onthe magnet plate of the rotor, of the bicycle headlamp according to thefirst embodiment of the present invention.

FIG. 8 is a view showing the relationship among the position of therotor attached on the spokes of the bicycle wheel, of the bicycleheadlamp according to the first embodiment of the present invention, thecycling speed, and the frequency of the generated power.

FIG. 9 is a perspective view showing the structure of the headlamp andthe illumination state, of the bicycle headlamp according to the firstembodiment of the present invention.

FIG. 10 is a view showing the positional relationship betweenlight-emitting diodes and condenser lenses of the bicycle headlampaccording to the first embodiment of the present invention.

FIG. 11 shows views of the structure of the condenser lenses used in thebicycle headlamp according to the first embodiment of the presentinvention: FIG. 11( a) is a side view of the condenser lenses; FIG. 11(b) is a rear view of the condenser lenses; and FIG. 11( c) is a frontview of the condenser lenses.

FIG. 12 is a view showing a test circuit including a resonant rectifiercircuit used in the bicycle headlamp 1 according to the first embodimentof the present invention.

FIG. 13 shows characteristic plots representing results obtained fromthe test circuit including the resonant rectifier circuit, which is usedin the bicycle headlamp 1 according to the first embodiment of thepresent invention, results obtained from a test circuit including aconventional double-voltage rectifier circuit, and results obtained froma test circuit including a conventional full-wave rectifier circuit:FIG. 13( a) shows plots obtained from the test circuit including theresonant rectifier circuit; FIG. 13( b) shows plots obtained from thetest circuit including the double-voltage rectifier circuit; and FIG.13( c) shows plots obtained from the test circuit including theconventional full-wave rectifier circuit.

FIG. 14 is a view showing speed-current plots representing therelationship between the current observed in FIG. 13 and the cyclingspeed.

FIG. 15 is a schematic diagram showing a headlamp electrical circuitaccording to a second embodiment of the present invention.

FIG. 16 is a schematic diagram showing a resonance circuit and a dc-dcconverter of a rectifying and smoothing circuit, in the headlampelectrical circuit according to the second embodiment of the presentinvention.

FIG. 17, is a schematic diagram showing a constant-current circuit inthe headlamp-electrical circuit-according to the second embodiment ofthe present invention.

FIG. 18 is a view showing the comparison between a conventionalnon-resonant power-generation curve and a resonant power-generationcurve obtained from the bicycle headlamp according to the firstembodiment and the headlamp electrical circuit according to the secondembodiment of the present invention: The horizontal axis indicates thenumber of revolutions, and the vertical axis indicates the electromotiveforce.

FIG. 19 is a waveform diagram showing voltage waveforms of differentcomponents of the headlamp electrical circuit according to the secondembodiment, used with the bicycle headlamp according to the firstembodiment of the present invention: The horizontal axis indicates time,and the vertical axis indicates voltage.

FIG. 20 is a view showing validity lines of the bicycle headlampaccording to the first embodiment of the present invention.

FIG. 21 is a schematic diagram showing the structure of a headlampelectrical circuit according to a third embodiment of the presentinvention, including a light sensor or a manual switch for turning thelight on or off.

FIG. 22 is a side view of a bicycle headlamp according to a fourthembodiment of the present invention, showing the attached state of aring-shaped magnet plate and the attached state of the headlamp.

FIG. 23 is a perspective view showing a bicycle headlamp according to afifth embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the present invention will be described with reference tothe figures.

FIGS. 1 to 17 are views showing a bicycle headlamp and a headlampelectrical circuit according to a first embodiment of the presentinvention.

FIG. 1 is a view showing the bicycle headlamp according to the firstembodiment of the present invention, namely, a side view showing aplurality of magnet plates attached to spokes of a bicycle wheel atparticular spacings.

FIG. 2 is a perspective view showing the bicycle headlamp according tothe first embodiment of the present invention, in which a stator,including a power-generating coil, is separated from a case.

FIG. 3 is an enlarged perspective view showing a rotor and the stator ofthe bicycle headlamp according to the first embodiment of the presentinvention.

FIG. 4 shows enlarged views of a part of the rotor of the bicycleheadlamp according to the first embodiment of the present invention:FIG. 4( a) is an enlarged front view of the magnet plate of the rotor;and FIG. 4( b) is an enlarged side view of the magnet plate of therotor.

FIG. 5 shows enlarged views of a magnet mounted on the magnet plate ofthe rotor of the bicycle headlamp according to the first embodiment ofthe present invention: FIG. 5( a) is a perspective view of the magnetmounted on the magnet plate of the rotor; FIG. 5( b) is a front viewshowing the magnet mounted on the magnet plate of the rotor; and FIG.5(c) is an enlarged front view of the magnet mounted on the magnet plateof the rotor.

FIG. 6 shows enlarged views of a power-generating coil of the stator ofthe bicycle headlamp according to the first 5 embodiment of the presentinvention: FIG. 6( a) is a front view of the power-generating coil ofthe stator; and FIG. 6( b) is a side view of the power-generating coilof the stator.

FIG. 7 is a view showing the positional relationship between the teethof the power-generating coil of the stator and the individual magnets onthe magnet plate of the rotor, of the bicycle headlamp according to thefirst embodiment of the present invention.

FIG. 8 is a view showing the relationship among the position of therotor attached to the spokes of the bicycle wheel, of the bicycleheadlamp according to the first embodiment of the present invention, thecycling speed, and the frequency of the generated power.

FIG. 9 is a perspective view showing the structure of the lens portionof the headlamp and the state of illumination, of the bicycle headlampaccording to the first embodiment of the present invention.

FIG. 10 is a view showing the positional relationship betweenlight-emitting diodes and condenser lenses of the bicycle headlampaccording to the first embodiment of the present invention.

FIG. 11 shows views of the structure of the condenser lenses used in thebicycle headlamp according to the first embodiment of the presentinvention: FIG. 11( a) is a side view of the condenser lenses; FIG. 11(b) is a rear view of the condenser lenses; and FIG. 11( c) is a frontview of the condenser lenses.

A bicycle headlamp 1 according to the first embodiment of the presentinvention can be broadly divided into a rotor 3, a stator 5, and a case7, as shown in FIGS. 1 and 2. The case 7, which will be described laterin detail, contains at least a headlamp electrical circuit 71, alight-emitting diode 73, a condenser lens 75, and a reflector 77.

The rotor 3 includes a plurality of magnet plates 33 attached to spokes91 of a wheel of a bicycle 9 at particular spacings along thecircumference of the wheel, each magnet plate having the form of an arcof a certain circle and including a plurality of magnets 31 disposed atregular circumferential spacings with alternating south and north poles.

The magnet plate 33 has a flat base plate 33 a having the form of an arcof a certain circle of radius r, a plurality of magnets 31 disposed onthe flat base plate 33 a at regular circumferential spacings withalternating south and north poles, and mounting holes 33 b provided inboth ends of the flat base plate 33 a, as shown in FIGS. 4( a) and 4(b).The flat base plate 33 a is made of a high-permeability material such asiron, preferably-high-permeability silicon steel. The magnets 31 mountedon the magnet plate 33 each have a length of 15 mm, a width of 6 mm, anda thickness of 4 mm, for instance, as shown in FIGS. 5( a) to 5(c), andare polarized in the direction of the thickness. The magnets 31 used inthis embodiment are made of Neodymium 40, which has a coercive force of3200 to 3500 Gauss (G).

With the magnet plates 33 attached to the wheel spokes 91 of the bicycle9 at particular spacings, as shown in FIG. 1, the rotor 3 and the stator5 enable intermittent power generation.

The stator 5 includes a case 51 of a power-generation unit with amounting block 51 a and a power-generating coil 53 disposed inside thecase 51 of the power-generation unit. When the mounting block 51 a ofthe case 51 of the power-generation unit of the stator 5 is mounted on afixed bracket 93 a of a front fork 93 of the bicycle 9, as shown in FIG.1, the power-generating coil 53 of the stator 5 faces the magnetic polefaces of the magnets 31 on the magnet plates 33 of the rotor 3 in afixed position, as shown in FIG. 3.

The power-generating coil 53 of the stator 5 includes a substantiallyE-shaped iron core 53 a and a coil 53 b wound on the middle projectingpart of the substantially E-shaped iron core 53 a, as shown in FIGS. 2,3, 6(a), and 6(b). The iron core 53 a is made of materials such as anamorphous material and silicon steel.

The magnets 31 on the magnet plate 33 of the rotor 3 are disposed almostat the same spacings as the teeth of the iron core 53 a in thepower-generating coil 53 of the stator 5, as shown in FIG. 7. A constantspacing of 5 mm, for instance, is kept between the surface of themagnets 31 of the magnet plate 33 of the rotor 3 and the surface of theteeth of the iron core 53 a of the power-generating coil 53 of thestator 5, as shown in FIG. 7.

The frequency of the generated power will be discussed below, supposingthat the magnet plate 33 of the rotor 3 is attached to the wheel spokes91 of the bicycle 9 in a certain positional relationship, with themagnets 31 of the magnet plate 33 of the rotor 3 and the teeth of theiron core 53 a of the power-generating coil 53 of the stator 5 disposedas described above.

Radius r1 (millimeters) of the wheel of the bicycle 9 of size X inchesis given by:r1=X/2×25.4   (1)If the radial distance between the rim of the wheel and the mountingposition of the magnet plate 33 on the wheel spokes of the bicycle 9 isd (millimeters), the mounting position r2 (millimeters) is expressed asfollows:r2=r1−d  (2)If d is 135 (position of mounting hole of the conventional roller-typebicycle generator), the frequency f (Hz) of the generated power iscalculated as follows:f=(V×10⁶×2π×r2)/(7200π×r1×2p)  (3)where V is the cycling speed (km/h) of the bicycle 9, and p is the pitch(mm) of the magnets 31.

The frequency f of the generated power with the bicycle 9 of size 24inches, 26 inches, and 28 inches can be calculated by substituting thefollowing values of r1 and r2 into expression 3. For instance, when thebicycle 9 of size 24 inches, of which r1 is 305 mm and r2 is 170 mm, istraveling at a standard speed (equals 15 km/h hereafter), the frequencyf of the generated power is 66.4 Hz. When the bicycle 9 of size 26inches, of which r1 is 330 mm and r2 is 195 mm, is traveling at thestandard speed, the frequency f of the generated power is 70.3 Hz. Whenthe bicycle 9 of size 28 inches, of which r1 is 355 mm and r2 is 220 mm,is traveling at the standard speed, the frequency f of the generatedpower is 73.9 Hz. The frequency f of the generated power described aboveor a frequency close thereto is obtained from the bicycle 9 traveling atthe standard speed if the magnets 31 of the magnet plate 33 of the rotor3 and the teeth of the iron core 53 a of the power-generating coil 53 ofthe stator 5 are disposed in the positional relationship as describedabove.

The case 7 will be described next. As shown in FIG. 2, the case 7contains at least the headlamp electrical circuit 71, the light emittingdiode 73, and the condenser lens 75. The headlamp electrical circuit 71,including a capacitor (described later) connected in series with thepower-generating coil 53 of the stator 5, can produce resonance at afrequency synchronized with a certain relative speed of the magnets 31of the rotor 3 and can rectify, smooth, and output power obtained fromthe power-generating coil 53. The light-emitting diode 73 is lit by thepower supplied from the headlamp electrical circuit 71. The condenserlens 75 focuses light produced by the light-emitting diode 73 in frontof the bicycle 9 and illuminates the roadway in front.

The headlamp electrical circuit 71 in the case 7 and thepower-generating coil 53 of the stator 5 are mutually connected by anelectrical wire 11, as shown in FIG. 2.

It is preferred that the light-emitting diode 73 contained in the case 7be a bullet-shaped white light-emitting diode with a luminous intensityof 2 cd or higher (NSPW312BS or NSPW300BS of Nichia Corporation) usedunder normal conditions. It is most favorable that a bullet-shaped whitelight-emitting diode with a luminous intensity of 6 cd or higher(NSPW500BS of Nichia Corporation) be used under normal voltage andcurrent conditions. The condenser lens 75 has such a focal length that acertain level of illumination is ensured at a specified distance.

More specifically, in this embodiment, two (a plurality of)light-emitting diodes 73 are used, and two condenser lenses 75 areprovided in the form of a dome. The two dome-shaped condenser lenses 75are aligned with the light-emitting diodes 73, as shown in FIGS. 10 and11.

Each dome-shaped condenser lens 75 has a curvature, a diameter, and athickness as indicated in FIGS. 10 and 11, that are calculated to obtaina certain level of illumination by focusing light in a specified circleat a specified distance, as shown in FIG. 9. A reflector 77 b or 77 c isprovided on a flat-plate portion above the condenser lens 75, as shownin FIGS. 9, 11(a), and 11(b), by applying a treatment for producingdiffused reflection to a component of the lens. The reflector 77 b or 77c makes it easier for other road users located ahead of the bicycle 9 tonotice the approach of the bicycle 9. More specifically, the opticalaxes of the light-emitting diodes 73 are aligned with the optical axesof the dome-shaped condenser lenses 75 so that light is gatheredefficiently.

The bicycle headlamp 1 according to the first embodiment of the presentinvention is designed to emit light of at least 5 lux in a circle havinga radius of 30 cm at a distance of 5 m ahead of the bicycle at thestandard cycling speed. The lens is shaped so that an object of about 10cm can be easily recognized at a distance of 10 m. These conditionscomply with a Japanese Industrial Standard (JIS) standard on bicycleheadlamps. In order to satisfy those requirements, the condenser lens 75has a thickness of about 10 mm, a curvature of 13.8, and a diameter of24.5 mm, for instance. The distance w between the axes of the twodome-shaped condenser lenses 75 and the distance W between the axes oftwo circles of light produced by the dome-shaped lenses at a certaindistance (5 m, for instance) have a relationship expressed by w=W.

As has been described above, the reflector 77 b or 77 c is providedabove the condenser lenses 75, as shown in FIGS. 9, 11(a), and 111(b),by applying a treatment for producing diffused reflection to the platecomponent of the lens. The reflector 77 b or 77 c makes it easier forother road users located ahead of the bicycle 9 to notice the approachof the bicycle 9.

The bicycle headlamp 1 uses a resonant rectifier circuit, as has beendescribed above. The resonant rectifier circuit will next be comparedwith other types of rectifier circuits.

FIG. 12 is a view showing a test circuit including the resonantrectifier circuit used in the bicycle headlamp 1 according to the firstembodiment of the present invention. The test circuit shown in FIG. 12includes the-following: the rotor denoted by the reference character 3,the magnets denoted by the reference character 31, the magnet platedenoted by the reference character 33, the power-generating coil denotedby the reference character 53, the iron core denoted by the referencecharacter 53 a, and the coil denoted by the reference character 53 b. Acapacitor C0 is connected in series with a diode D2, and they areconnected to both ends of the power-generating coil 53 b, as shown inFIG. 12. The cathode of the diode D2 is connected to the anode of adiode D1, and the cathode of the diode D1 is connected to one end of aparallel circuit of a load and a smoothing capacitor C1. The other endof the parallel circuit of the load and the smoothing capacitor C1 isconnected to the anode of diode D2. A 15-ohm resistor and twolight-emitting diodes used in the present invention are connected inseries, and this circuit is connected in the forward-bias direction asthe load.

FIG. 13 shows characteristic plots representing results obtained fromthe test circuit including the resonant rectifier circuit used in thebicycle headlamp 1 according to the first embodiment of the presentinvention, a test circuit including a conventional double-voltagerectifier circuit, and a test circuit including a conventional full-waverectifier circuit: FIG. 13( a) shows plots obtained from the testcircuit including the resonant rectifier circuit; FIG. 13( b) showsplots obtained from the test circuit including the double-voltagerectifier circuit; and FIG. 13( c) shows plots obtained from the testcircuit including the conventional full-wave rectifier circuit.

The average current I in FIG. 13( a) is larger than the average-currentI in FIG. 13( b) or FIG. 13( c).

The relationship between the current obtained as described above and thecycling speed of the bicycle 9 is represented by the speed-current plotsshown in FIG. 14. The horizontal axis indicates the speed in km/h, andthe vertical axis indicates the current flowing through the load.

The FULL-WAVE RECTIFIER plot shown in FIG. 14 indicates that when thefull-wave rectifier circuit is used, a small current is obtained at alow cycling speed, and the current increases in proportion to thecycling speed.

The DOUBLE-VOLTAGE RECTIFIER plot shown in FIG. 14 indicates that alarger current can be obtained at a low cycling speed with thedouble-voltage rectifier circuit than with the full-wave rectifiercircuit or the resonant rectifier circuit, and the current obtained atan increased cycling speed is smaller than that with the two other typesof circuits.

If the resonant rectifier circuit is used in the bicycle headlampaccording to the first embodiment of the present invention, the currentobtained at a low speed is smaller than the current obtained with thedouble-voltage rectifier, as the RESONANT RECTIFIER plot in FIG. 14shows. However, at a speed exceeding a certain level (about 11 km/h inthe figure, for example), the current increases with an increase inspeed, and exceeds the current obtained with the double-voltagerectifier. In addition, when another level of speed (26 km/h in thefigure, for example) is exceeded, the current does not exceed a certainlimit. That is, a speed exceeding a certain level does not cause thegenerated power to increase in an analogous fashion, so that anexcessively large current will not flow through the load.

These characteristics indicate that the resonant rectifier circuit usedin the bicycle headlamp 1 according to the first embodiment of thepresent invention is effective.

It is easily understood that power is generated intermittently becausethe magnet plates 33 of the rotor 3 are disposed, as described above, atparticular spacings on the wheel spokes 91 of the bicycle 9 in thebicycle headlamp and the headlamp electrical circuit using the resonantrectifier circuit. A headlamp electrical circuit according to a secondembodiment of the present invention appropriately smoothes out even thepower generated intermittently, as described above, and can supplydirect-current power containing a very small amount of ripple. Thestructure and the effects will be described below.

FIGS. 15 to 19 are views provided to describe the headlamp electricalcircuit according to the second embodiment of the present invention.

FIG. 15 is a schematic diagram showing the headlamp electrical circuitaccording to the second embodiment of the present invention. FIG. 16 isa schematic diagram showing a resonance circuit and a dc-dc converter ofa rectifying and smoothing circuit, in the headlamp electrical circuitaccording to the second embodiment of the present invention. FIG. 17 isa schematic diagram showing a constant-current circuit in the headlampelectrical circuit according to the second embodiment of the presentinvention.

The headlamp electrical circuit 71 according to the second embodiment ofthe present invention can be broadly divided into a resonance circuit711 and a rectifying and smoothing circuit 713, as shown in FIGS. 15,16, and 17. The rectifying and smoothing circuit 713 can be divided intoa dc-dc converter 713 a and a constant-current circuit 713 b, as shownin FIGS. 16 and 17.

The resonance circuit 711 includes the power-generating coil 53 of thestator 5 and capacitor C0 connected in series with the power-generatingcoil 53. The coil 53 b of the power-generating coil 53 and capacitor C0establish resonance at a frequency synchronized with a certain relativetraveling speed of the magnets 31 in the direction indicated by thearrow shown in the figure (this has been explained with reference toFIG. 8).

The rectifying and smoothing circuit 713 is configured to rectify andsmooth out the power obtained from the power-generating coil 53 of theresonance circuit 711 and to supply the power to the light-emittingdiodes 73.

The dc-dc converter 713 a of the rectifying and smoothing circuit 713 isconfigured to rectify the power obtained from the power-generating coil53 of the resonance circuit 711 by means of diodes D1 and D2, and tosmooth out the power by means of a smoothing capacitor C1.

The constant-current circuit 713 b of the rectifying and smoothingcircuit 713 includes at least two transistors TR1 and TR2, two resistorsR1 and R2, and a capacitor C2, and is configured to receive the directcurrent obtained from the dc-dc converter 713 a and to supply a certainamount of current to the light-emitting diodes 73.

The structures of the resonance circuit 711 and the dc-dc converter 713a will next be described in further detail, with reference to FIGS. 15and 16. The capacitor C0 is connected in series with thepower-generating coil 53 to form a series resonance circuit. The anode Aof the diode D1 is connected to one end of the power-generating coil 53.One end of the capacitor C0 connected in series is connected to theanode A of the diode D2, and the cathode K of the diode D2 is connectedto the anode A of the diode D1. The smoothing capacitor C1 has apositive (+) terminal connected to the cathode K of the diode D1 and anegative (−) terminal connected to the anode A of the diode D2.

In this circuit, the rotation of the magnet plates 33 of the rotor 3induces an alternating-current electromotive force in thepower-generating coil 53. If the frequency determined by the spacingsbetween the magnets of the magnet plate 33 and the number of revolutionsmatches the resonance frequency of the LC circuit, resonance of the LCcircuit allows power to be efficiently obtained from the electromotiveforce induced in the power-generating coil 53.

By specifying the capacitance of the capacitor C0 and the inductance ofthe power-generating coil 53 such that the resonance frequency is closeto the frequency determined by the standard speed, an overcurrent can besuppressed at a higher speed. The technical means for the configurationdescribed above provides a series resonance circuit for improving theefficiency of power generation by the power-generating coil.

The configuration of the constant-current circuit 713 b will bedescribed next. The positive (+) terminal of the smoothing capacitor C1is connected via the-resistor R1 to the collector (C) of the NPNtransistor TR1, the base (B) of the NPN transistor TR2, and the positive(+) terminal of the capacitor C2. The negative (−) terminal of thesmoothing capacitor C1 is connected to the negative (−) terminal of thecapacitor C2, the emitter (E) of the transistor TR1, and one end of theresistor R2. The base (B) of the transistor TR1 is connected to theemitter (E) of the transistor TR2 and to the other end of the resistorR2. One output terminal of the constant-current circuit 713 b is thepositive (+) terminal of the smoothing capacitor C1, and the otheroutput terminal is the collector (C) of the transistor TR2.

The functions of the bicycle headlamp according to the first embodimentand the headlamp electrical circuit 71 according to the secondembodiment of the present invention will be described next withreference to FIGS. 18 to 20, on the basis of FIGS. 1 to 11 and FIGS. 15to 17.

FIG. 18 is a view showing the comparison between a conventionalnon-resonant power-generation curve and a resonant power-generationcurve obtained from the bicycle headlamp according to the firstembodiment and the headlamp electrical circuit according to the secondembodiment of the present invention: The horizontal axis indicates thenumber of revolutions, and the vertical axis indicates the electromotiveforce.

FIG. 19 is a waveform diagram showing voltage waveforms of differentcomponents of the headlamp electrical circuit according to the secondembodiment, used with the bicycle headlamp according to the firstembodiment of the present invention: The horizontal axis indicates time,and the vertical axis indicates voltage.

FIG. 20 is a view showing validity lines of the bicycle headlampaccording to the first embodiment of the present invention.

When the bicycle 9 travels, the wheels turn, rotating the rotor 3including the magnet plates 33 disposed at particular spacings on thewheel spokes 91. This induces an electromotive force intermittently inthe power-generating coil 53 of the stator 5. (When the magnet plate 33of the rotor 3 faces the power-generating coil 53 of the stator 5, poweris generated. When the space between the magnet plates 33 of the rotor 3faces the power-generating coil 53 of the stator 5, no power isgenerated.)

The bicycle headlamp 1 and the headlamp electrical circuit 71 accordingto the present invention are configured so that the power-generatingcoil 53 of the stator, and the resonance circuit 711 formed of thepower-generating coil 53 and the capacitor C0 establish series resonanceat the standard speed of the bicycle 9. Therefore, the electromotiveforce induced in the power-generating coil 53 becomes as indicated byplot a in FIG. 18: The electromotive force surges while the speedincreases from a low level to the standard level, and the increase inelectromotive force becomes moderate after the standard speed isexceeded.

It is known that, in contrast, the conventional bicycle headlampincreases the electromotive force in proportion to the speed, asindicated by plot b in FIG. 18.

The electromotive force induced in the power-generating coil 53 of thestater 5 is stored in the smoothing capacitor C1, by the action of thediode D1 and the capacitor C0 and the action of the diode D2 and thesmoothing capacitor C1. Voltage V1 across the ends of the smoothingcapacitor C1 has characteristics as indicated by plot V1 in FIG. 19.

Because the direct-current output of the smoothing capacitor C1 is avoltage containing a large amount of ripple, as represented by plot V1in FIG. 19, the output is supplied from the positive (+) terminal of thesmoothing capacitor C1 via the resistor R1 to the positive (+) terminalof the capacitor C2, the collector (C) of the transistor TR1, and thebase (B) of the transistor TR2, and is returned from the emitter (E) ofthe transistor TR1, the negative (−) terminal of the capacitor C2, andthe other terminal of the resistor R2 to the negative (−) terminal ofthe smoothing capacitor C2.

A voltage V1 containing a large amount of ripple in the direct-currentoutput passes through the resistor R1 and is integrated in the capacitorC2 having a small capacitance, and a phase lag is produced. The currentflowing between the collector (C) and emitter (E) of the transistor TR2is controlled by supplying the base (B) of the transistor TR2 with aripple voltage V2 in opposite phase (see plot V2 in FIG. 19).

The current control is performed in opposite phase with a ripple voltageacross the light-emitting diodes 73 connected in series with thecollector (C) of the transistor TR2, so that the ripple of the current Iflowing through the light-emitting diodes 73 connected in series issignificantly reduced, as indicated by plot I in FIG. 19. The resistor,R2, connected between the emitter (E) of the transistor TR2 and thenegative (−) terminal of the smoothing capacitor C1, causes negativefeedback, which reduces the ripple further.

When the current flowing through the transistor TR2 increases to bring avoltage V3 across both ends of the resistor R2 above the cut-off voltageof the transistor TR1, a current flows through the transistor TR1,causing the resistor R1 to decrease the base voltage (V3) of thetransistor TR2, thus decreasing the current flowing through thetransistor TR2. Because the current flowing through the light-emittingdiodes 73 is limited, the series-connected light-emitting diodes 73 canbe protected from overcurrent.

It was determined whether the bicycle headlamp 1 according to the firstembodiment of the present invention conforms to a Japanese IndustrialStandard (JIS) standard on bicycle headlamps. A dc constant-currentpower supply and a light meter were used as test instruments complyingwith JIS C 9502. The test dc constant-current power supply supplied thelight-emitting diodes 73 of the bicycle headlamp 1 with the same voltageand the same current provided by the headlamp electrical circuit 71.Illumination was measured by the test light meter placed in thepositions shown in FIG. 20. In FIG. 20, position A was a directextension of the axis of the lens, and positions B to E were 30 cm awayfrom position A. The test light meter was placed in positions A to E tomeasure illumination.

When the light-emitting diodes 73 passed a current of 25 mA, theillumination at point A was 135 cd, the illumination at point B was 92.3cd, the illumination at point C was 119 cd, the illumination at point Dwas 124 cd, and the illumination at point E was 121 cd. The illuminationat points B to E averaged 114 cd.

When the light-emitting diodes 73 passed a current of 30 mA, theillumination at point A was 155 cd, the illumination at point B was 104cd, the illumination at point C was 136 cd, the illumination at point Dwas 141 cd, and the illumination at point E was 138 cd. The illuminationat points B to E averaged 130 cd.

The JIS standard specifies that the illumination at point A should be400 cd or higher and that the illumination at points B to E shouldaverage 100 cd or higher. This means that the average illuminationsatisfies the requirement.

The JIS standard also specifies that the color of light emitted from thebicycle headlamp 1 should be white or pale yellow and should be asindicated in the JIS table. The bicycle headlamp according to the firstembodiment of the present invention emits white light conforming to theJIS standard.

The bicycle headlamp 1 according to the first embodiment and theheadlamp electrical circuit 71 according to the second embodiment of thepresent invention have the following advantages:

(1) The contactless generator enables power to be generated withoutfrictional resistance, which is encountered by the conventionalroller-type dynamo, and the cyclist's power needed during cycling can besignificantly reduced.

(2) The capacitor C0 is connected in series with the power-generatingcoil 53 in order to establish series resonance at the standard cyclingspeed of the bicycle 9, with the result that the efficiency of powergeneration of the bicycle headlamp according to the present invention is50% higher than that of the conventional non-resonant bicycle headlamp.

(3) Because the resonance frequency is specified corresponding to thestandard cycling speed, the power generated at a cycling speed exceedinga certain level can be suppressed. The current is suppressedaccordingly, and the light-emitting diodes 73 can be protected.

(4) Because the rectifying and smoothing circuit is configured toamplify the capacitance of the capacitor C1, the capacitance requirementis reduced to 1/10 or lower. Because a feedback circuit is provided, acurrent limit can be specified.

(5) The dome-shaped condenser lenses are aligned with the optical axesof the light-emitting diodes and focus light effectively, so that thebicycle headlamp 1 can provide an illumination of at least 5 lux in acircle having a radius of 30 cm at a distance of 5 m ahead of thebicycle at a standard cycling speed.

In addition, the bicycle headlamp according to the present invention canprovide illumination sufficient for recognizing an object of about 10 cmat a distance of 10 m. The reflector 77 b or 77 c provided above thecondenser lenses 75 by applying a treatment for producing diffusedreflection makes it easier for other road users located ahead of thebicycle to notice the approach of the bicycle 9. This helps preventtraffic accidents.

(6) Because the stator 5 and the case 7 of the bicycle headlamp 1according to the first embodiment are separated, the case 7 can beattached to a desired position, such as a handlebar.

FIG. 21 is a schematic diagram showing the structure of a headlampelectrical circuit according to a third embodiment of the presentinvention, including a light sensor or a manual switch for turning thelight on or off.

FIG. 21 shows that a light sensor 13 and/or a manual switch 15 is addedto the constant-current circuit 713 b of the rectifying and smoothingcircuit 713.

In the constant-current circuit 713 b, the light sensor 13 is connectedbetween the base (B) of the transistor TR2 and the emitter (E) of thetransistor TR1 connected via the resistor R2, or between the collector(C) and the emitter (E) of the transistor TR1. The transistor TR2 turnson or off in accordance with a sense signal from the light sensor. Thisallows or interrupts current supply to the light-emitting diodes 73.

In the constant-current circuit 713 b, the manual switch 15 may beconnected between the base (B) of the transistor TR2 and the emitter (E)of the transistor TR1 connected via the resistor R2, or between thecollector (C) and the emitter (E) of the transistor TR1. The transistorTR2 turns on or off in accordance with the on/off signal sent from themanual switch. This allows or interrupts current supply to thelight-emitting diodes.

In the constant-current circuit 713 b, both the light sensor 13 and themanual switch 15 may be connected in series or in parallel, between thebase (B) of the transistor TR2 and the emitter (E) of the transistor TR1connected via the resistor R2, or between the collector (C) and theemitter (E) of the transistor TR1. The transistor TR2 turns on or off inaccordance with either or both of the signal sent from the light sensorand the signal sent from the manual switch. This allows or interruptscurrent supply to the light-emitting diodes 73.

The headlamp electrical circuit according to the third embodimentenables automatic turn-on and turn-off, depending on the ambient light,and the manual switch 15 also enables on/off control as desired.Accordingly, no operation is required to start power generation.

FIG. 22 is a side view of a bicycle headlamp according to a fourthembodiment of the present invention, showing the attached state of aring-shaped magnet plate and the attached state of the headlamp.

The fourth embodiment shown in FIG. 21 will be described using the samereference characters as shown in the first to third embodiments for thesame members as used in the embodiments.

In the bicycle headlamp according to the fourth embodiment of thepresent invention, the rotor 3 has a ring-shaped magnet plate 33attached to the wheel spokes 91 of the bicycle 9 along the circumferenceof the wheel, as shown in FIG. 22.

An electromotive force is continuously induced in the power-generatingcoil 53 of the stator 5. The power generated continuously can beappropriately averaged by the bicycle headlamp 1 according to the firstembodiment and the headlamp electrical circuit 71 according to thesecond embodiment of the present invention. Therefore, thelight-emitting diodes 73 can be continuously lit.

FIG. 23 is a perspective view showing a bicycle headlamp according to afifth embodiment of the present invention.

A bicycle headlamp 1A according to the fifth embodiment of the presentinvention includes an integral unit combining the stator 5 and the case7, as shown in FIG. 23. The case 7 contains the stator 5 which includesthe power-generating coil 53, the headlamp electrical circuit 71, thelight-emitting diodes 73, the condenser lenses 75, and the reflector 77.A reference character 7 a denotes a mounting block used to attach theheadlamp on the fixed bracket 93 a.

Because the stator 5 and the case 7 are combined, the integral bicycleheadlamp 1A can be attached to existing position normally used formounting the bicycle headlamp and can be easily replaced.

INDUSTRIAL APPLICABILITY

According to the present invention, the contactless generator asdescribed above enables power to be generated without frictionalresistance, which is encountered by the conventional roller-type dynamo,and the cyclist's power needed during cycling can thus be significantlyreduced.

According to the present invention, a capacitor is connected in serieswith the power-generating coil in order to establish series resonance,with the result that the efficiency of power generation becomes 50%higher than that of the conventional non-resonant bicycle headlamp.

According to the present invention, the resonance frequency is specifiedcorresponding to the standard cycling speed, so that the amount ofcurrent flowing at a cycling speed exceeding a certain level can besuppressed, and the light-emitting diodes can be protected.

According to the present invention, a constant-current circuit that canamplify the capacitance of the capacitor C1 is configured, so thatsmoothing can be appropriately performed even if a large ripple ispresent. In addition, a current limit can be specified at the same time.

According to the present invention, the lamp can be turned on or offautomatically depending on the ambient light and can also be turned onor off when desired by a simple operation.

According to the present invention, the dome-shaped lens aligned withthe optical axis of each light-emitting diode focuses light effectively,so that a certain level of illumination can be obtained in a circle at aspecified distance.

1. A bicycle headlamp comprising: a rotor comprising a plurality ofmagnet plates attached to spokes of a bicycle wheel along thecircumference of the wheel, each magnet plate having a form of an arc ofa certain circle and comprising a plurality of magnets disposed atregular circumferential spacings with alternating south and north poles;a stator comprising a power-generating coil comprising a coil and aniron core disposed in a fixed position to face the magnetic pole facesof the magnet plates of the rotor; and a case separated from the stator,or for containing all of the stator, wherein the case contains at leasta headlamp electrical circuit comprising a resonance circuit formed ofthe power-generating coil of the stator and a capacitor connected inseries with the-power-generating coil, and having, as a resonantfrequency, a power-generation frequency determined by the positionswhere the magnets and the power-generating coil are disposed, when thebicycle is pedaled at a predetermined speed, and a rectifying andsmoothing circuit for rectifying, smoothing, and outputting electricpower obtained from the power-generating coil of the resonance circuit,a plurality of light-emitting diodes that are lit by the electric powersupplied from the headlamp electrical circuit, and a condenser lens forfocusing light emitted from the plurality of light-emitting diodes infront of the bicycle and for illuminating the roadway, wherein the lensis a dome-shaped lens disposed for each of the plurality oflight-emitting diodes, the dome-shaped lens has a curvature, a diameter,and a thickness calculated to obtain a specified level of illuminationin a specified circle at a specified distance by focusing light; and areflector is provided on a flat-plate portion above the lens, byapplying a treatment for producing diffused reflection, so thatapproaching of the bicycle can be noticed ahead of the bicycle.
 2. Abicycle headlamp according to claim 1, wherein the stator, comprisingthe power-generating coil, the headlamp electrical circuit, theplurality of light-emitting diodes, and the condenser lens are containedin the case as a unit.
 3. A bicycle headlamp according to claim 1,wherein the headlamp electrical circuit, the plurality of light-emittingdiodes, and the condenser lens are contained in the case; and thestator, comprising the power-generating coil, is separately disposedoutside the case.
 4. The bicycle headlamp according to claim 1, whereinthe predetermined speed is 15 km/h.
 5. A bicycle headlamp according toclaim 1, wherein the stator comprises the magnet plates attached to thespokes of the bicycle along the circumference of the wheel, in acontinuous ring shape or in separate positions.
 6. A bicycle headlampaccording to claim 5, wherein the stator, comprising thepower-generating coil, the headlamp electrical circuit, the plurality oflight-emitting diodes, and the condenser lens are contained in the caseas a unit.
 7. A bicycle headlamp according to claim 5, wherein theheadlamp electrical circuit, the plurality of light-emitting diodes, andthe condenser lens are contained in the case; and the stator, comprisingthe power-generating coil, is separately disposed outside the case.
 8. Abicycle headlamp according to claim 1, wherein the plurality oflight-emitting diodes include a white light-emitting diode with aluminous intensity of 2 cd or higher, and the lens has a focal lengthsuch that a certain level of illumination is ensured at a specifieddistance.
 9. A bicycle headlamp according to claim 8, wherein thestator, comprising the power-generating coil, the headlamp electricalcircuit, the plurality of light-emitting diodes, and the condenser lensare contained in the case as a unit.
 10. A bicycle headlamp according toclaim 8, wherein the headlamp electrical circuit, the plurality oflight-emitting diodes, and the condenser lens are contained in the case;and the stator, comprising the power-generating coil, is separatelydisposed outside the case.